The M2 Browing .50 cal (12.7mm) delivered a 43.3 gram shell at 880 m/s, with a 750-850 rpm. That's against the MG131 13mm which delivered a 36 gram shell at 730 m/s at 900 rpm.
MG131 fires more but is slower and lighter.
The Hispano Mk.II 20mm delivered a 130 gram shell at 880 m/s, with a 600 rpm. Against a MG151/20 20mm delivering a 105 gram shell 725 m/s, at 700 - 750 rpm.
MG151/20 fires more but, again, is slower and lighter.
I'd still rather have the Spitfire armament although they were more equal in fighter vs. fighter than I previously thought.